The math:
Pj Problem of Interest is of type force (push and pull). However in this case, compression is more pronounced. Hence the choice of force-push.

Formulas of interest:
Modulus of resilience ur, is strain energy absorbed per unit volume.
ur = (σpl)1/2/(2E)---------(1)
Proportional limit is the maximum stress a material can sustain without deviating from the law of stress-strain proportionality.
σpl is stress at proportional limit
E is modulus of elasticity.